ADeceXrPmr3m-}      Enzymes  and  Their  Importance.  555 
of  this  form  of  chemical  work.  To-day,  however,  the  inception  and 
course  of  numerous  reactions  in  the  living  substance,  which  were 
formerly  incomprehensible,  can  only  be  grasped  by  the  assumption 
of  enzymatic  processes — the  enzymes  have  assumed  a  part  of  the 
functions  formerly  attributed  to  "  vitality." 
We  are,  however,  in  the  same  position  with  regard  to  the  enzymes 
as  with  electricity — we  know  its  action  and  utilise  it,  but  are  ignor- 
ant of  its  real  nature.  Nobody  has  as  yet  held  a  pure  enzyme  in 
his  hand,  and,  as  with  electricity,  there  are  two  points  of  view : 
(i)  the  minority  see  in  enzymatic  reactions  only  an  exhibition  of 
a  special  form  of  energy,  and  (2)  others  maintain  that  they  are  of 
a  material  nature.  From  the  results  of  some  experiments  on  the  lac- 
case  of  Kurushi  and  other  materials  from  the  protein  reaction  of  the 
substance,  and  the  fact  that  pyrrol  is  formed  when  it  is  heated  with 
alkalies,  in  addition  to  the  impossibility  of  separating  the  enzyme 
itself  from  gummy  substances,  Professor  Tschirch  assumes  as  a 
provisional  working  hypothesis  that  the  enzymes  are  glucoproteids 
of  the  pyrrol  group;  but,  .as  he  states,  this  assumption  may  be  right 
or  wrong,  and  does  contribute  much  towards  explaining  enzymatic 
actions.  Of  greater  importance  is  the  recognition  of  the  colloid 
character  of  all  enzymes ;  indeed,  their  action  is  only  comprehensible 
on  this  basis  in  cases  where  several,  often  antagonistic,  effects  are 
displayed  side  by  side  in  the  same  cell.  There  can  be  no  doubt  that 
not  only  in  the  animal,  but  also  in  the  plant  organism,  in  the  same 
cell  several — indeed,  many — enzymes  are  present,  of  which  some — 
e.g.,  reductases  and  oxydases,  glucoside-splitting  and  glucoside-form- 
ing— act  in  direct  opposition  to  each  other. 
It  is  now  established  that  the  enzymes,  like  the  catalysts,  hasten 
the  course  of  a  reaction,  that  they  are  destroyed  by  heating  to  700- 
ioo°  C,  and  that  they  can  be  "  poisoned  "  by  certain  substances. 
On  the  other  hand,  the  presence  of  certain  substances  (some  metals, 
traces  of  acids  and  alkalies)  enhance  their  action,  but  it  is  still  doubt- 
ful whether  and  to  what  extent  the  enzymes  as  such  participate  in 
reactions,  and  whether,  as  is  now  generally  assumed,  the  enzyme 
is  not  used  up  in  the  reaction,  but  before  its  effect  sets  in  it  enters  into 
an  adsorption  combination  with  the  substratum. 
The  fundamental  properties  of  the  enzymes  were  known  to 
Schomein,  who  discovered  the  oxidising  ferments  in  the  'sixties  of 
the  past  century,  although  in  1809  Gottling,  a  pharmacist,  had  ob- 
served the  peculiar  oxydase  reactions  of  gum  acacia,  without  being 
